Many things will be required for a rapid advance in crop yields: more water for irrigation and more skillful application of that water, land drainage in many places, better seeds and methods of cultivation, more fertilizers and pesticides skillfully applied. Also required are a host of social, economic, and institutional changes, most importantly the shift from subsistence agriculture to the market economy. The "Green Revolution" requires heavy application of purchased inputs, such as fertilizer, pesticides, hybrid seeds, and often machinery and fuel. More favorable land tenure arrangements; the incentive of adequate prices for crops; extension and educational programs; adequate credit; better handling, storage, and distribution systems will be needed. Suitable combinations of measures which are designed specifically for both the soil conditions and the social situations in each less developed region are called for.
The problem posed by rapidly increasing populations is to make the necessary cultural and technical changes rapidly enough to stay ahead of the problem and raise standards of living at the same time. Few countries have attained increases in farm output of more than 4 percent per year; none of the developed countries has exceeded 4 percent for more than 5 or 6 years; yet a 3 percent annual increase in population wipes out most of even such a rapid rate of improvement. That the less developed countries can attain even greater rates of advance is shown, however, by Mexico's achievement in the last 14 years—1952-1966: a phenomenal 6 percent annual increase in agricultural output outdistanced a population growth rate of 3.33 percent per year, making possible an increase in farm output per capita of 2.5 percent annually.
The returns from India and a few other countries indicate that new seeds recently developed, in combination with other factors, have greatly raised yields where they are most needed. The story of miracle rice and wheat is beginning to unfold. More extensive utilization of world fisheries is helping to raise the level of protein nutrition in the world, as world catches rise about 6 percent per annum, nearly three times as rapidly as other foods and feeds. Resort to algae culture, and even petroleum and coal, as food sources may become practicable with further scientific and technical improvements. However, for the next few decades at least, the world cannot count on these farther-out possibilities for large contributions to its food supplies.
Institutional and material changes in production methods in the less developed countries could provide sufficient food in nearly all regions of the world. There are, of course, local situations in which the resource base is severely limiting, but few of these are likely to be so restrictive as to prevent a high degree of self-sufficiency. Some of the highest ratios of population to land (total area or agricultural land area) are in Japan and western Europe (see Table 3); yet these regions produce an average of about 80 percent of their food supplies. The cost of the imported 20 percent of the food supplies for these areas is about equal to the cost of their fuel imports, requiring 15 to